At my range we have:
Me and a couple more with 260
Buddy with 6.5 Creedmore
Buddy with 6.5x47 (Lapua)

The number one difference is in accuracy, there is no difference.
The number two difference is in velocity, there is little difference in velocity. Of course projectile weight being the same vs barrel length vs those other external influences.

Lastly the biggest difference is I like my 260 because I compete in our "tactical" matches against the buddy with 6.5x47 (Lapua) and when I win I want it clear that it's the shooter not the caliber. When he wins he praises his DTA, I praise my DIY Weatherby Custom.

Basically, there is so little difference it all depends on you and your preference. The buddy with the 6.5x47 (Lapua) and DTA is very 'brand' conscious. I on the other hand prefer to buck the brand trend and analyze what works. The buddy with the 6.5 Creedmoore likes Savage rifles and chose the one in the middle.